When sewing a workpiece with a sewing machine, the layout of the patterns are typically determined by taking a certain spacing from the edges of the workpiece or from an existing pattern on the workpiece. For instance, the user may wish to sew stitches arranged in a straight line that is located at a certain spacing from the edge of the workpiece. To address such requirements, sewing machines have been proposed that is provided with a marking unit that is configured to irradiate reference marks on the sewing machine bed or the workpiece so that location of patterns such as straight stitches or the location of the workpiece can be determined based on the reference mark.
One example of such marking device employs two marking lamps that irradiate cruciform reference marks on the workpiece that indicate the start position and the end position of the straight stitch. In more detail, the marking unit primarily comprises a frame, and adjustment base, an end-point marking lamp and a start point marking lamp. The frame extends in the direction in which the workpiece is fed and the end-point marking lamp is secured on one end of the frame. The start-point marking lamp is provided movably on the frame by way of the adjustment base. The start-point marking lamp, provided on the adjustment base, is moved with the adjustment base which is driven by a step motor. Marking unit is further provided with a counter for inputting the distance, in other words, the amount of movement of the start-point marking lamp.
The counter comprises an input unit provided with buttons for specifying the amount of movement of the start-point marking lamp through numerical input and a display unit for displaying the inputted amount of movement. During the sewing operation, the user is to input the amount of movement of the start-point marking lamp, which is given by the distance between the start point and the end point, through the buttons provided at the input unit. Responsively, the step motor is driven in accordance with the inputted distance to move the start-point marking lamp.
The marking unit, however, requires the user to make numerical inputs of distance through the input unit in order to move the reference mark, that is, to move the marking lamps which can be cumbersome to the user. Further, the location of the irradiated reference mark needs to be verified through the user's eyes and if the reference mark is not located as desired, the numerical input and verification cycle needs to be repeated until the reference mark is properly located, which is again, cumbersome to the user.